Many managers of investment portfolios employ risk modeling as a management technique. In order to determine the risk of a portfolio, consideration may be given to: (1) the holdings of the portfolio; (2) a factor exposure matrix; (3) a factor covariance matrix; (4) the specific volatility of each stock in the portfolio. The factors may include, for example, style factors, industry factors, and/or country factors. The factor covariance matrix may include undesirable biases that are incorporated into the data that it presents.